1. Field of the Invention
The present invention relates to a lateral pushing type push-button switch which is to be used in a small electronic apparatus such as a portable telephone, a digital camera, a PDA, or a portable audio player.
2. Description of the Prior Art
Conventionally, a lateral pushing type push-button switch is known in which a pressing force in a lateral direction (horizontal direction) is converted to a longitudinal direction (vertical direction) (for example, see Japanese Patent Application Laying-Open No. 2006-244977). FIGS. 9 to 12 show such a conventional push-button switch.
In FIGS. 9 to 12, the reference numeral 1 denotes a housing which is made of an insulating material such as a synthetic resin, and which is formed into a box-like shape having an accommodating portion 1a and an opened upper face. In the inner bottom of the accommodating portion 1a, a pair of stationary contacts 2a, 2b which are configured by a conductive metal plate are integrally embedded by a method such as insert molding so that the contacts are partly exposed from the inner bottom face. External terminal 3a, 3b which are led out from the pair of stationary contacts 2a, 2b are projectingly formed in lower portions of paired opposed side faces of the housing 1, respectively. A window portion 1b communicating with the accommodating portion 1a is disposed in another side face of the housing 1. Engaging projections 1c which are outward projected are formed in the four corner of the housing 1, respectively.
A movable contact 4 which is configured by a conductive thin metal plate, and which is curved in a dome-like shape so as to be invertible is placed above the paired stationary contacts 2a, 2b in the accommodating portion 1a. The movable contact 4 is placed in a state where the lower face of a dome top portion is opposed to the one stationary contact 2a exposed from the inner bottom face with maintaining a predetermined gap therebetween, and an edge portion of the outer periphery of the dome is contacted with the other stationary contact 2b exposed from the inner bottom face of the accommodating portion 1a (this contacted state is not shown in FIG. 9).
A dust-proof sheet 5 which is configured by an insulative resin sheet member such as polyamide resin is disposed on the upper face side of the movable contact 4. A peripheral edge portion of the dust-proof sheet 5 is placed on the upper face of the accommodating portion 1a of the housing 1 and fixed by an adhesive agent or the like so as to cover the opening of the accommodating portion 1a, thereby preventing dust, a foreign material, and the like from entering the contact portions in the accommodating portion 1a. 
The reference numeral 6 denotes an operating member made of an insulating material such as a synthetic resin, and having: a pressing portion 6a which is projected from the window portion 1b of the housing 1; an actuating portion 6b which is projected from the pressing portion 6a into the accommodating portion 1a; and a slide portion 6d which is formed in continuous with the pressing portion 6a so as to surround the both sides and rear of the actuating portion 6b through an opening 6c that is disposed in the periphery of the actuating portion 6b. The operating member 6 is placed on the upper face side of the dust-proof sheet 5 placed in the accommodating portion 1a. The pressing portion 6a is projected from the window portion 1b of the housing 1. A butting portion 6e which is a free end of the actuating portion 6b is opposed to the upper face of the dome top portion of the movable contact 4 across the dust-proof sheet 5. The slide portion 6d is slidably accommodated in the accommodating portion 1a. 
The reference numeral 7 denotes a cover which is formed by stamping and bending a metal plate, and which has: an upper plate 7a that is attached to an upper portion of the housing 1, and that is formed in a flat plate-like shape so as to cover the accommodating portion 1a; and four attachment legs that are bent substantially perpendicularly from four edges of the upper plate 7a to hang in an L-shape, respectively. Engaging pieces are disposed at the tip ends of the attachment legs, and engaged with the engaging projections 1c disposed in the four corners of the housing 1, respectively, whereby the cover 7 is attached to the upper portion of the housing 1.
A guiding portion is formed in a substantially middle of the upper plate 7a. The guiding portion is bent into the accommodating portion 1a of the housing 1, and butts against the butting portion 6e of the actuating portion 6b of the operating member 6 to guide the actuating portion 6b in the pressing direction of the movable contact 4. The guiding portion is configured by: an inclined portion 7d formed by a slope of about 45 degrees which is formed by bending the plate face of the upper plate 7a into the accommodating portion 1a of the housing 1 along the pressing direction of the operating member 6; and a pair of connecting portions 7e which have a substantially triangular shape, which are disposed in continuous to the both sides of the inclined portion 7d, and which are connected to the upper plate 7a. When the cover 7 is attached to the upper portion of the housing 1, the inclined portion 7d and the connecting portions 7e are positioned in an opening 6c disposed in the slide portion 6d of the operating member 6. At this time, the inclined portion 7d is opposed to the butting portion 6e (free end) of the actuating portion 6b of the operating member 6. Rear end sides of the inclined portion 7d and connecting portions 7e which are bent into the opening 6c are cut away, to prevent the inclined portion 7d and the connecting portions 7e from butting against the rear end of the opening 6c of the slide portion 6d when the slide portion 6d slides in the accommodating portion 1a. 
The guiding portion is formed in the cover 7 in the following manner. First, a cutout 7f which is slightly thin is formed by press or the like at a position of the upper plate 7a of the cover 7 which will be formed as the rear end of the guiding portion. Next, a portion in front of the cutout 7f is downward bent at about 45 degrees by press or the like, thereby forming the inclined portion 7d, and the pair of connecting portions 7e which are continuous to the sides of the inclined portion 7d, and which have a substantially triangular shape.
In the conventional push-button switch having the above-described configuration, in an initial state shown in FIG. 9, the butting portion 6e (free end) of the actuating portion 6b of the operating member 6 butts against the upper face of the dome top portion of the movable contact 4 through the dust-proof sheet 5, and the pressing portion 6a is urged in the leftward direction in the figure (opposite to the pressing direction of the pressing portion 6a) to be outward projected, by a synergistic action between the upward elastic urging force of the movable contact 4, and the slope of the inclined portion 7d of the cover 7. At this time, in the movable contact 4, the edge portion of the outer periphery is contacted with the stationary contact 2b, but the lower face of the dome top portion is separated from the stationary contact 2a, so that the switch is in the OFF state.
When, in this state, the pressing portion 6a is pressed in the rightward direction in the figure, as shown in FIG. 12, the butting portion 6e (free end) of the actuating portion 6b is guided along the inclined portion 7d in the downward direction in the figure (the direction perpendicular to the pressing direction of the pressing portion 6a), and presses the upper face of the dome top portion of the movable contact 4 through the dust-proof sheet 5, whereby the movable contact 4 is downward inverted. Then, the lower face of the dome top portion of the movable contact 4 is contacted with the stationary contact 2a, and the stationary contacts 2a, 2b are electrically connected with each other, so that the switch is in the ON state.
When the pressing to the pressing portion 6a is released in this state, the movable contact 4 is upward inverted and returned by an inversion returning force of the movable contact 4 itself, and the switch is in the OFF state. By the urging force exerted at this time, the butting portion 6e of the actuating portion 6b is oppositely urged along the inclined portion 7d in the leftward direction in the figure (the direction opposite to the pressing direction of the pressing portion 6a), and the pressing portion 6a is outward projected to be returned to the initial state.